1. Field of the Invention
This invention is in the field of blood processing and more specifically relates to plasmapheresis.
2. Description of the Prior Art
Whole human blood includes at least three types of specialized cells. These are the red blood cells, white blood cells, and platlets. All of these cells are suspended in plasma, a complex aqueous solution of proteins and other chemicals.
Until relatively recently, blood transfusions have been given using whole blood. There is, however, growing acceptance within the medical profession for transfusing only those blood components required by a particular patient instead of using a transfusion of whole blood. Transfusing only those blood components necessary preserves the available supply of blood, and in many cases, is better for the patient. Before blood component transfusions can be widely employed, however, satisfactory blood separation techniques and apparatus must evolve.
Plasmapheresis is the separation of whole blood into a plasma component and a non-plasma component under conditions whereby the plasma component is retained and the non-plasma component is returned to the donor. Presently, plasmapheresis is achieved on a large scale using satellite pouch systems. A variety of satellite pouch plasmapheresis systems have been patented, and some typical examples are those systems described in U.S. Pat. No. 3,190,546 to Raccuglia et al.; U.S. Pat. No. 3,211,368 to Shanley; and U.S. Pat. No. 3,545,671 to Ross. With such systems, whole blood is withdrawn from a donor and flows to a pouch containing anticoagulant. The pouch is then disconnected from the donor phlebotomy line, centrifuged, and the supernatant plasma fraction is expressed into a connected plasma pouch. The pouch containing the non-plasma component is then reconnected to the phlebotomy system so that the non-plasma component can be returned to the donor.
It has become customary with satellite pouch systems to carry out this sequence of steps twice for each donor. Typically, one unit, or about 500 ml. of whole blood, is withdrawn, anticoagulated and separated. Approximately 250 ml. of plasma component is obtained and the non-plasma component is returned to the donor. Subsequently, another unit of whole blood is withdrawn and processed. Using such techniques with satellite pouch systems, it takes approximately 85 minutes to obtain 500 ml. of separated plasma component and to return the non-plasma component to the donor. Because the blood pouch is disconnected from the donor at the end of each withdraw cycle, there is always the danger of returning blood components to a donor which are not his own. Satellite pouch systems also require careful attention during each of the processing cycles to produce consistently high quality plasma.